Preventative conservation

Of prime importance to the collection manager are the creation of a stable environment for the collection and its careful storage, handling and display – preventing damage and deterioration before it happens.

Environmental conditions and storage

By keeping track of the condition of your museum, you can plan for the best ways to preserve and protect every single object and it will also help you spot problems the moment they arise.

The six main environmental factors which you should be thinking about within your institutions are:

• Light
• Ultraviolet (UV) radiation
• Relative humidity (RH), the amount of moisture in the air
• Temperature
• Pests
• Pollution

As artworks can be made up of a variety of materials, it is best to bear in mind the following recommended environmental conditions which involve light, UV and RH:

• Light levels should not exceed 50–80 lux for works on paper, as it bleaches pigments and discolours the paper.
• Light levels should not exceed 150–200 lux for oil paintings and other organic materials such as lacquerware, plastics, wood, horn, bone and ivory.
• Stone, ceramic, metal and glass are relatively insensitive to light, so levels can be up to 300 lux.
• Ultraviolet levels should be at or below 75 microwatts/lumen. Ultraviolet radiation, present in sunlight and some artificial light sources, is particularly damaging and should be filtered out if possible (e.g. by coating windows with UV-absorbent film and using non-UV artificial light sources).
• Hours of exposure to light is calculated on the basis of the recommended annual light exposure for the particular material in question. As light damage is cumulative, periods of brighter illumination can be 'cancelled out' by cutting out light when it is not needed.
• Make sure to eradicate all sources of light from storage areas when they are not in use.
• Relative humidity should be kept as stable as possible within a 20% band. This allows for annual seasonal changes in humidity and the needs of a mixed collection. A band as wide as 40–65% RH is fine, and it should not exceed 65% as mould, mildew and pests are more likely to occur. Changes in temperature and relative humidity also affect all organic materials, such as paint, canvas and wood. They shrink and expand, and warp and distort, in response to such changes. In the case of paintings, this can affect the adhesion of the paint to the ground and support, can split wooden panels and frames and in extreme cases encourage mould. Rapid daily or weekly changes are worse for paintings than slow seasonal changes.
• Museums are generally heated to human comfort levels of around 17–21°C but stores can be kept at lower temperatures to slow down the deterioration of objects, to around 10–15°C, colder if human comfort is not an issue. Therefore, a museum should try to maintain temperatures between 10–21°C. It is important to maintain stable temperatures rather than allowing them to fluctuate, particularly in the short term, like from day to night, as this causes greater damage to the collections.

In short and general terms, stability is the key. Fluctuations in any of the above environmental factors can cause damage to objects so that is why it is important to keep all the environmental data, collate and analyse it in order to act upon anything which appears out of the norm. It is also recommended to be maintained in a systematic way and retained for a minimum of five years. This will not only help in explaining any slow changes in object deterioration, but it is also needed for funding applications and future loan requests and accreditation.

A researcher examines a painting

To clean or not to clean sculpture

A simple surface clean will often produce a dramatic visual result and may be all the work that is necessary to improve the condition of a sculpture. This type of cleaning can be broken down into two main types – dry methods and wet methods.

Dry methods

A high level of footfall will result in a significant amount of dust and this will not only affect the visual appearance of sculptures, but due to dust deposits attracting moisture, these can also become bonded to surfaces and cause the works to deteriorate over time. Removing the dust early will not only ensure that the sculptures are looking their best but will help to make sure they survive in good condition for generations to come.

This is something which, in most instances, can be carried out in-house and if regularly maintained, not require the assistance of a trained conservator.

What you will need:

• A vacuum cleaner with adjustable suction and a HEPA filter.
• Soft natural-bristle brush or brushes – hog hair and pony hair are commonly used.
• A piece of netting, gauze or old tights.
• A rubber band.

Method of use:

• Secure the netting over the vacuum nozzle using the rubber band. This will stop the object or any decorative or loose elements from being sucked inside the vacuum bag.
• Use the soft natural-bristle brush, goat's hair and pony hair are most commonly used, to brush the dirt, lint or dust towards the low-suction of the vacuum but make sure the vacuum nozzle is not placed directly onto the surface of the object itself.
• The ferrules of brushes (the part that holds the bristles) should be bound with masking or insulating tape to pad them so that they can't scratch or damage the object.
• Brushes should be labelled with a material type (wood, metal, paper etc.) and they should only be used for that type of material. This avoids damaging an object by scratching it with particles from another material or depositing dirt onto another object.
• Dust from the top of the sculpture downwards.
• Use a gentle sweeping or flicking motion to lift the dirt off and away from the surface and into the suction of the vacuum.
• Brush along the grain or similar to lift dirt out of the crevices.
• Brushes should be washed after use. Use a mild, liquid, detergent, such as Stergene or Woolite. Massage the detergent into the bristles and rinse under a tap. Allow to air dry.

If the dust and dirt appear to be bound more closely to the surface and is not coming away easily, then you may be required to use a method which comes into direct contact with the sculpture such as a smoke sponge or eraser. These methods can only be used on stable surfaces such as stone, plaster, unglazed but not powdery ceramics, tiles, paper and wood.

Smoke sponges are sponges impregnated with chemicals that act as a dry detergent, bonding with and removing the dust and dirt. Cut a small piece from the smoke sponge. Use it dry and gently stroke it over the dirty area. Be careful to support the sculpture so that cleaning does not tear or cause damage by the movement of the sponge. Rotate the piece of sponge as it gets dirty and wash after use with Stergene or Woolite as they can be reused several times before throwing them away.

Wet methods

If the dirt layer does not appear to be coming off with any of the dry methods, or there still seems to be dirt bound to the surface, then a wet method may need to be applied. It is important to note that these methods do have some dangers attached and can result in surface coatings being removed, colours bleeding and the activation of corrosion.

This is why it is so imperative that you test your solvent on a small, inconspicuous area first, wait for the area to completely dry before assessing the surface to make sure there is no clouding, discolouration, colour movement, removal of any surface coatings or other negative change. If you see anything happening out of the ordinary, then do not continue.

What you will need:

• Water – general washing of objects and removal of dirt from intricate surfaces and removing organic adhesives.
• Acetone – evaporates very quickly and so good for objects that should not be wetted. It is useful for removing oil, grease and adhesive residues, and also cleaning broken edges before repair.
• Methylated spirit – does not wet as much as water but evaporates more slowly than acetone, which means it can penetrate dirt layers for effective removal.
• White spirit – does not affect as many surface finishes as acetone and meths, but it does have a very pungent smell. It is useful for degreasing and dirt and dust removal.
• Spit – an active ingredient salivary amylase, an enzyme. It is useful for dirt and dust removal.

Method of use:

All wet methods are usually carried out by applying the solvent to the sculpture using a swab. This can be a purchased cotton bud, or a hand-rolled swab which allows you to make exactly the size swab required and is cheaper than buying off the shelf ones.

When cleaning, the swab should be rolled across the surface and disposed of as soon as they are dirty. Never put a used swab back into the solvent. If you have used a detergent as well, then the surface should be rinsed by going over the area with a swab of plain solvent to remove the detergent. The used swabs need to be disposed of in a container that allows the solvent to evaporate slowly, which can be a jam jar with a hole pierced into the lid. Push the swab into the hole and pull out against an edge of the hole, as this pulls the cotton bud off the stick leaving it safely confined to the jar. Once the solvent has evaporated completely the swabs can be placed in a bin.

Cleaning paintings

Oil paintings and frames can be dusted with a clean and very soft brush if it is absolutely certain there is no flaking or raised paint. Never use a vacuum cleaner or a cloth that may catch upon the edges of cracks or vulnerable impasto. When cleaning glass, always spray glass cleaner onto the cloth, not the glass.

A transit frame

Moving and handling

Always use clean hands, or better still clean gloves, when carrying artworks.

The gloves most commonly used are either 100% cotton gloves or Nitrile disposable gloves. Both are safe to be worn in the handling of most materials, but in some instances, the cotton gloves may not provide the necessary grip or get caught on rough or uneven surfaces. They are also permeable so can wick sweat and oil from the skin and deposit this onto the object. It is advisable not to wear the cotton gloves with the little rubberised dots on the palms as these can imprint and leave residue on fragile surfaces such as highly polished bronzes.

The nitrile gloves are favoured over their latex version due to sensitivities and allergies in some people. They protect against a broad spectrum of chemicals and are generally the gloves of choice for most curatorial work.

When handling paintings, hold by the frame, with the painting facing towards you. Use two hands, one to hold the edge and the other to support it from beneath, and two people if necessary. Some frames and their gilded surfaces can be very fragile in themselves. Always use padding or foam when resting the painting on the ground or against a wall.

For sculptures, the best way to mitigate risk is to eliminate or minimise the need for handling or movement and this can be achieved by having bespoke carry cases, storage boxes and skates made which will save you from physically handling the sculpture from one location to another. It also minimises damage being caused to yourself.

Making a dynamic risk assessment

There will always be a time when you need to handle an artwork and the best way to approach it is by carrying out a dynamic risk assessment and ask yourself: Who? What? When? Where? How?

Who will be handling the object or how many people are required for the move?

What type and number of objects are to be moved? What are the sculpture or painting's inherent properties and how does this dictate the materials and equipment needed?

When is the best time to carry out the move? How long will it take and is it best to do it out of visiting hours?

Where is the object now? Where will its final location be? What is the best route to take?

How will the final solution be implemented and understood by all those involved?

An oil painting well packed for transport

Packing and transport

Works of art are always best packed and transported by specialist art movers. These firms are necessarily expensive but are essential for valuable and fragile works. However the advice here may be helpful for packing and moving less valuable works.

The purpose of packing for transport is to protect the painting or sculpture from physical and environmental shocks and accidents during moving and associated storage and, if necessary, to allow for mechanical handling by forklift trucks etc.

If the painting is glazed with glass, the first consideration is to protect it should the glass break during transit. This is traditionally done by taping the glass. Taping of glass should be done using wide, low-tack tape (such as masking tape, not parcel tape) applied in overlapping strips, folding over the ends and avoiding contact with the frame. Taping should be removed immediately after transit as it can be difficult to remove later. Taping is not necessary, and can be harmful, for Perspex (acrylic) glazing.

Wrapping first in polythene will help to protect the painting from changes in relative humidity. But never allow packing materials to touch the picture surface.

Further packing options depend on the risk, distance and length of the journey to be packed for.

The minimum packing would be to wrap the corners of the frame with bubble pack or thin sheets of foam and wrap a layer of polythene or bubble wrap around the whole painting. This would be suitable for moving within a building or for a short accompanied van trip.

Next would be a 'transit' frame. This is a lightweight but structurally sound wooden frame, deeper than the painting's own frame (if it has one), within which the painting can be screwed using its mirror plates. The whole transit frame is then wrapped in polythene.

Safest and securest is a packing case or crate. The sturdy wooden case is lined with polyethylene or polyurethane foam to the precise size of the picture frame and the wrapped painting is placed in the case and a foam-lined lid screwed down, ensuring the frame cannot move within the case. Handles are advisable.

Transport

Professional fine art movers use air-conditioned vans; good packing and short journeys will reduce the risks of environmental problems. Wrapped paintings and crates should always be securely strapped to the sides of the van, with frames well protected from straps or cords.

Handle and transport paintings vertically (except when closing or opening a packing case), and with the right orientation (i.e. the top of the painting to the top and mark the outside of the case accordingly). However large portraits are often more safely handled and transported on their sides.

Displaying paintings

Paintings in public spaces should be glazed if possible to avoid accidental damage. For maximum security, a painting will be hung with mirror plates attached to the sides of the frame at the back and screwed to the wall (invisible high-security fixings are also available). Hanging a painting on wire and a picture hook is not recommended for visual, conservation and security reasons, and for heavier paintings is very risky.

Always avoid hanging in direct sunlight, and also avoid hanging above radiators or other heat sources, under bright or hot lights, opposite doors and windows and in busy corridors.

Information about further guidance and resources can be found on our page of useful links.